The usual way this decision gets made is simple: get an air quote, get a sea quote, notice air is several times more expensive per kilo, and book sea. That instinct is right often enough that people stop questioning it — and wrong often enough to matter.
What the freight rate leaves out
Capital tied up in transit
Sea freight from South China to Mombasa is roughly 28 to 40 days port to port. Add supplier lead time, consolidation, clearance and inland delivery and you can be looking at two months between paying your supplier and having sellable stock. Air compresses that to a week or two.
Every day of that gap is money you have spent and cannot yet recover. If your business is financed by an overdraft or a facility, that carrying cost is real and quantifiable. If it is financed from your own working capital, the cost is everything else you could not buy with it.
Safety stock
Long, variable lead times force you to hold more buffer stock to avoid running out. Short lead times let you hold less. Buffer stock is inventory you have paid for and are not selling.
Being out of stock
The cost that never shows on an invoice. A fast-moving line that runs dry for three weeks does not simply defer those sales — some of them go to a competitor permanently.
Handling, insurance and damage
Sea shipments, particularly LCL, involve more handling and more opportunities for damage and pilferage. Insurance premiums reflect that. Air moves faster with fewer touches.
When air genuinely wins
- High value density — electronics, phone accessories, pharmaceuticals, jewellery. When freight is a small fraction of goods value, speed is cheap.
- Fast-moving or seasonal lines — where being late means being irrelevant.
- Product launches and restocks — where a stockout costs more than the freight difference.
- Samples and pre-production — never worth waiting six weeks for.
- Perishables and anything with a shelf life.
When sea is clearly right
- Low value density — furniture, building materials, packaging, bulk raw materials.
- Predictable, planned replenishment where the lead time is designed into your ordering cycle.
- Large volumes where the per-unit gap is simply too wide to bridge.
The hybrid most people miss
You do not have to choose one for everything. A common pattern that works well: move the bulk of a line by sea, and air a small proportion to cover the gap while the sea shipment is in transit. You get most of the cost advantage of ocean freight with much of the responsiveness of air.
The other hybrid worth knowing is sea-air, where cargo moves by ocean to a hub such as Dubai and flies the final leg. It sits between the two on both cost and time and suits some cargo well.
How to actually decide
Work out, per unit: the freight cost difference, the number of extra days sea adds, the value of the goods, and your cost of capital. Multiply the tied-up value by the extra days at your financing rate. Add an honest estimate of stockout risk. Then compare.
You will find some product lines flip to air that you assumed were permanently sea cargo — and you will find others where sea wins by a margin so wide the question does not arise. Both answers are useful.
We are happy to run this calculation with you for your specific goods. It takes a short conversation and it regularly changes how people ship.